The introduction of the UC Torana in 1978 saw the demise of the V8 engines. The greatly rationalized choices were now the 2·85 L six for the S and SL sedans, or the 3·3 L inline six for the SL sedan and hatch.
There were at one point design ideas of a 5-door hatchback version of the UC, which had a similar side profile to the Rover SD1 and rode an extended wheelbase, although they never got past the clay modelling stage.
There was also a UC SL/T hatch turbo model built. Only 3 cars were made, they were basically a 3.3litre engine and 4 speed manual with a small NGM Turbocharger and SU carburettor fitted.
But by now the Torana was too similar in size to the more modern Holden Commodore, and it was soon dropped from the Holden range in 1979. Sunbirds continued through 1980 with the 1·9 L Starfire (based on the 2·85 L six) replacing the Opel unit. For a while at least, there was talk of further extending the Torana/Sunbird's production life beyond 1980, with a facelifted 'UD' model, although it never eventuated.